Electric motors are being installed ever more frequently in modern motor vehicles. Electric motors are installed in particular as drive motors that are fully integrated into the drive train or they are installed in hybrid applications by way of example as starter generators. Separately excited synchronous machines that comprise a rotor composed of a lamination stack that is provided with an exciter winding are sometimes used. The ends of the exciter winding are guided over two slip rings that are arranged on the rotor shaft. The exciter voltage is applied to the exciter winding by way of carbon brushes. The two slip rings together with the base body that is supporting said slip rings are frequently also referred to simply as “slip ring”.
Rotating electric machines of this type are encumbered with the problem that abraded particles of the carbon brushes penetrate in the form of electrically conductive dust particles into the inside of the machine. These dust particles can deposit themselves by way of example as a conductive layer on the machine elements and can cause electrically conductive leakage paths.
The document DE 100 14 310 A1 discloses an electric machine having a floating gap seal for the purpose of sealing the housing inner space of the electric machine. Although a gap seal of this type can hinder the penetration of dust into the housing inner space, it is still necessary to protect the housing inner space in an improved manner against the penetration of brush dust.
The document DE 10 2008 041 650 A1 describes an electric machine having a fan that comprises protruding fan blades for the purpose of distributing the air, as a consequence of which abraded brush dust is carried away from the slip rings together with the air.